Babies understand fairness by 15 months

Babies as young as 15 months can recognise when someone is being treated unfairly and respond by being generous towards them, scientists have found.

Babies as young as 15 months can recognise when someone is being treated unfairly  Photo: Alamy

As well as being able to tell whether people are being treated even handedly, babies just over a year old are capable of basic altruism, or trying to help others even at their own expense.

Being able to sense that a situation is unequal made babies more willing to share their favourite toys, a new study found, suggesting that fairness and altruism are linked.

Previous research had shown that two-year-olds could help others and that at about six or seven children have a sense of fairness, but a new experiment indicated that the traits may develop even earlier.

Researchers tested 47 babies by showing each a video in which a researcher unevenly distributed food between two people, followed by a similar film in which the food was shared equally.

Babies pay greater attention when something surprises them and the scientists found that overall they spent more time looking at the screen if one recipient had been given more food than the other.

Jessica Sommerville, of the University of Washington in the US, who led the study, said: "Our findings show that these norms of fairness and altruism are more rapidly acquired than we thought.

"The infants expected an equal and fair distribution of food, and they were surprised to see one person given more crackers or milk than the other."

In a second experiment, where the babies were given two toys and a researcher indicated they would like to have one, two thirds of the infants offered to share.

Some 92 per cent of those who offered up their preferred toy, named "altruistic sharers", had also spent more time looking at the unfair distribution of food during the earlier video.

In contrast 86 per cent of those shared their least preferred toy – dubbed "selfish sharers" – had been more surprised and paid more attention when food was divided fairly.

Writing in the PLoS ONE journal, the researchers said this showed the altruistic sharers had been sensitive to the unfairness of the food video, while the selfish sharers showed almost the opposite effect.